9.String to Integer (atoi)

Example 1:
Input: "42"
Output: 42

Example 2:
Input: "   -42"
Output: -42
Explanation: The first non-whitespace character is '-', which is the minus sign.
             Then take as many numerical digits as possible, which gets 42.

Example 3:
Input: "4193 with words"
Output: 4193
Explanation: Conversion stops at digit '3' as the next character is not a numerical digit.

Example 4:
Input: "words and 987"
Output: 0
Explanation: The first non-whitespace character is 'w', which is not a numerical 
             digit or a +/- sign. Therefore no valid conversion could be performed.

Example 5:
Input: "-91283472332"
Output: -2147483648
Explanation: The number "-91283472332" is out of the range of a 32-bit signed integer.
             Thefore INT_MIN (−231) is returned.

Solution:

Corner Cases: 1. Remove Whitespaces 2. Check sign 3. Check validity 4. Check min and max range

class Solution
{
public:
    int myAtoi(string str)
    {

        int i = 0;
        int res = 0;
        int sign = 1;
        int k = 0;
        while (str[i] == 32) // Remove whitespaces
        {
            i++;
        }

        if (str[i] == '-') // Check for sign
        {
            sign = -1;
            i++;
        }
        else if (str[i] == '+')
        {
            sign = 1;
            i++;
        }

        while (i < str.length())
        {
            if (str[i] >= '0' && str[i] <= '9') // Check for validity
            {
                // Checking for max and min
                if (res > INT_MAX / 10 || (res == INT_MAX / 10 && str[i] - 48 > 7))
                {
                    if (sign == 1)
                    {
                        return INT_MAX;
                    }
                    else if (sign == -1)
                    {
                        return INT_MIN;
                    }
                }
                k++;
                res = res * 10 + (str[i] - 48);
            }
            else
            {
                break;
            }

            i++;
        }

        if (k == 0)
        {
            return 0;
        }

        return res * sign;
    }
};